1. Field
The present description relates to the field of sockets for microelectronic and micromechanical chip packages, and, in particular to modifying the connections between a die package and a system board using the socket or nearby components.
2. Related Art
Many computer and electronic systems, microprocessors and other electronic and micromechanical die or chips are held in a package. The package containing the die or chip is then attached to a supporting system using a socket. The socket is mounted to a motherboard, system board, logic board, printed circuit board (PCB), or a similar device. The board, being significantly larger than the package and the socket is typically constructed from lower cost, lower density materials that are capable of enduring higher mechanical and electrical stresses.
As a result of the materials used for the board, it is expensive or impossible to support a large number of electrical connections in a small space. As a result, the pins of the socket that connect to the board must maintain some level of spacing in order to meet the desired electrical and cost goals. This also requires that the package for the die also maintain the same level of spacing.
With the increasing pin counts for microprocessors, central processing units (CPU's), and other electronics and micromechanical devices, the supporting packages and sockets must be made larger in order to maintain the same spacing between connections. Otherwise the pins are too close together to meet the desired electrical and cost goals of the system board.
The larger package and socket sizes result in higher costs for the die or chip and the corresponding package. If instead the pin pitch on the PCB side of the socket is reduced, more advanced technology for the PCB is required to route the signal lines and provide proper via clearances. This more advanced technology increases costs for the socket and the system board. Additionally, a smaller pitch on the socket with present socket technology makes the socket more difficult or impossible to manufacture with the existing technology.
In current microprocessors, the die may have a bump pitch of about 150-250 μm, while the package's connection to the socket as a LGA (Land Grid Array), BGA (Ball Grid Array) or PGA (Pin Grid Array) may have a solder ball pitch of 1000-1270 μm. The system board will have the same pitch. The ball pitch of 1000 μm or more and the supporting structure make the socket large compared to the die. A die of 15 mm×15 mm may require a package of 37.5 mm×37.5 mm. This is more than six times larger than the die. The additional size of the package to match the socket increases the cost of manufacturing and distributing the packaged dies.